PHYSICS OF NONLINEAR FIBER COUPLERS

A simple qualitative description of nonlinear couplers is presented whereby the maximum and minimum values of core power are immediately apparent from a graphical representation, here called the power flow portrait. Each coupler has a characteristic portrait, revealing its unique physics. We believe that this approach is novel to all branches of nonlinear theory. Full details are given for nonlinear couplers with cores composed of different materials, Kerr law being a special case only. The study is motivated from the familiar perspective of linear couplers and is augmented by a comprehensive quantitative description leading to new analytical results.